Theoretical studies on interactions between Ni2+ and glycylglycine

Theoretical calculations were performed to study the interactions between Ni2+ and glycylglycine by density functional theory using the B3PW91 functional and optimize coordinated complexes at the singlet, triplet and quintet states with eight complexes of every state found. The ground states of those complexes are all triplet states. In the triplet complexes, the oxygen atom and nitrogen atom of glycylglycine were coordinated with Ni2+ to form di- and tridentate compounds. In gas phase, the stablest complex is the structure I-3. The solvent effects were also taken into consideration and discussed. The results show that the structure (VIII)-V-3, a zwitterionic species, is the complex in solvent phase. In solvation progress, the electrostatic interactions between the zwitterionic species and solvent may play very important role.